Structure and tribological properties of reactively sputtered Zr–Si–N films

Zr–Si–N films were deposited on silicon and steel substrates by magnetron sputtering of a Zr–Si composite target in Ar–N2 reactive mixtures. The silicon concentration in the films was adjusted in the 0–7.6 at.% range by varying the surface of Si chips located on the erosion zone of the target. The films were characterised by X-ray diffraction, electron probe microanalysis, atomic force microscopy and wear tests. The structure and the tribological properties of Zr–Si–N films were compared to those of ZrN coatings. Depending on the silicon concentration, the films were either nanocomposites (nc-ZrN/a-SiNx) or amorphous. Introduction of silicon into the zirconium nitride coatings induced a change in the preferential orientation of the ZrN grains: [111] for ZrN films and [100] for Zr–Si–N ones. This texture modification was also observed for a ZrN film deposited on an amorphous SiNx layer. Thus, within our deposition conditions, the occurrence of a-SiNx enhanced the [100] preferred orientation. Friction and wear behaviour of the films were carried out against spheres of alumina or 100 Cr6 steel by using a ball-on-disc tribometer. The results showed that addition of silicon into ZrN-based coating induced a strong decrease in the friction coefficient and in the wear rate compared to those of ZrN films. These results were discussed as a function of the films structure and composition.